I can't remember the times we set when DDs were that age - probably 8ish, but they were in bed at whatever o'clock and could then read for a 1/2 hour before lights out
They were always allowed up for an extra 1/2 hour on the weekend evenings, ie. Thurs and Friday here, Fri/Sat in UK. Maybe that will help with any rule setting. Also am sure if she says ALL her friends are allowed that will not be true ;) !
Also DD1 was allowed up a bit later than DD2 - a 1/2 hour.
I now let DDs self regulate up to a point as they're pretty sensible with it and have realised that staying up too late after 10 doesn't work on school nights - they're 14 and 17.
It's also worth saying no mobile phones in bedrooms at night I think as then the temptation isn't there to be texting into the wee small hours! Even if they say they'll switch them off... Haven't done this with mine but wish I had in hindsight, but I do now feel that they are the ones who suffer if they don't do this, not me!!